Polyesters of 4,4&#39;-hexafluoroisopropylidene diphenol

ABSTRACT

RELATES TO A UNIQUE THERMALLY STABLE POLYMER THAT US PARTICULATE USEUL IN PROTECTIVE COATING COMPOSITIONS AND PAINTS SYSTEMS. THE POLYMER IS PREPARED BY AN INTERFACIAL POLYMERIZATION PROCESS AT ROOM TEMPERATURE WHEREIN HEXAFLUOROACETONE BISPHENOL A IS MIXED IN ONE PHASE AMD ISO AND/OR TEREPHTHALOYL CHLORIDE IS MIXED IN THE OTHER PHASE IN THE PRESENCE OF A SUITABLE TERMINATOR. VARIOUS PROPORTIONS OF THE HEXAFLUOROACETONE BISPHENOL A AND THE PHTHALOLY CHLORIDE OPTIONALLY REPLACED BY VARIOUS SPECIFIED DIFUNCTIONAL INTERMEDIATES.

United StatesPatent O U.S. Cl. 260-47 6 Claims ABSTRACT OF THEDISCLOSURE Subject disclosure relates to a unique thermally stablepolymer that is particularly useful in protective coating compositionsand paint systems. The polymer is prepared by an interfacialpolymerization process at room temperature wherein hexafluoroacetoneBisphenol A is mixed in one phase and iso and/or terephthaloyl chlorideis mixed in the other phase in the presence of a suitable terminator.Various proportions of the hexafiuoroacetone Bisphenol A and thephthaloyl chloride are optionally replaced by various specifieddifunctional intermediates.

The invention described herein may be manufactured and used by or forthe Government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

This is a continuation-in-part of patent application Ser. No. 89,516filed Nov. 13, 1970, now abandoned, which is a continuation-in-part ofapplication Ser. No. 612,299, filed Jan. 26, 1967, now abandoned.

Presently available polymers exhibit various deficiencies as coatingsfor modern supersonic types of aircraft. Silicones maintain theirintegrtiy at high temperatures but require a baking cycle to developoptimum properties. Acrylics are excellent in weathering resistance butare deficient in low temperature performance. Epoxies chalk and yellowduring outdoor exposure. Urethanes have utility to only about 350 F.Vinyls exhibit poor resistance to high temperatures and jet lubes. Hightemperature polymers such as polyimides and polybenzimidazoles discolorand require a baking cycle to develop full properties.

It is therefore a principal object of the invention to providea noveland improved polyester which withstands severe weathering, repeatedexposure to jet lubes and fuels, and extreme temperature variations.

, It is a further object of the invention to provide a novel andimproved high temperature polyester which is soluble in relativelynon-toxic solvents, and may be applied in the form of a spray that driesquickly in air.

It is a further object of the invention to provide a novel and improveduse for a polymer as a protective paint material particularly foraerospace vehicles.

Other objects and advantages will appear in the more detaileddescription set forth hereinbelow, it being understood, however, thatthis more detailed description is given by way of illustration andexplanation only, and not by way of limitation, since various changestherein may be made by those skilled in the art without departing fromthe scope or spirit of the invention.

In accordance with the invention, a room temperature interfacialpolymerization method is used to prepare the improved high molecularweight polymer. The interfacial polymerization process is apolycondensation at room temperature between two fast reactingintermedaites in separate liquid phases. Due to its relatively lowtemperature of reaction, the resulting polymer is superior in many waysto a melt condensation product in that the possibility of crosslinkingand polymer decomposition are reduced.

Patented July 16, 1974 ice After many runs of this type were made andthe resulting end product polymers were evaluated, it was found thathighly satisfactory results were obtained when hexafiuoroacetoneBisphenol A and various phthaloyl chlorides were used as intermediateswith a thermally stable polymer terminator such as benzoyl chloride. Theformula for the reaction when hexafiuoroacetone Bisphenol A,isophthaloyl chloride, and terephthaloyl chloride were combined toobtain the improved polyphenylester polymer of the invention, shownwithout the terminator, is as follows:

Acid chlorides of other stable structure difunctional intermediates suchas 2,6-naphthaloyl chloride, 4,4'-bibenzoyl chloride and oxy4,4'-dibenzoyl chloride were also used with the hexafiuoroacetoneBisphenol A with good results. Best solubility in non-toxic paintsolvents such as the aromatics, ketones and esters was obtained whenterephthaloyl chloride constitutes somewhat less than 40% of the totalacid or phthaloyl chlorides. Varying quantities of the hexafiuoroacetoneBisphenol A were also replaced by such intermediates as Bisphenol A,other Bisphenols, 4, 4'-dihydroxydiphenyl, 4,4-dihydroxydiphenylmethane, 4, 4-dihydroxydiphenyl ether and other dihydroxy aromaticcompounds with satisfactory results. Superior jet lube resistance wasobtained when from 10 to 30% of the hexafiuoroacetone Bisphenol A wasreplaced with Bisphenol A. It was found that monofunctional polymerchain terminators were necessary with these aromatic type polyesters sothat the polymers would not degrade with loss of properties over aperiod of time, while in solution. The preferred coating or paintsolvent system contained relatively non-toxic toluene, xylene andanisole. Solvents containing any active hydrogen materials also degradedthe polymers.

It was further found that the isothermal high temperature heatresistance of the polymers was significantly improved when terminatorswere used. Mono-functional polymer chain thermally stable terminatingintermediates such as diphenyl carbamoyl chloride, benzoyl chloride,naphthaloyl chloride, ter-butyi phenol, para-phenyl phenol and otherfunctionally similar thermally stable aromatic or heterocyclicmonofunctional materials were also used to terminatethe polymers.

The resistance of certain of these improved fluoro- Bisphenol A polymersto prolonged exposure at 500 F. and sunlight and weathering resistance,as well as high solubility in non-toxic paint solvents and resistance todeterioration in the presence of jet fuels and lubricants were alsofound to be particularly useful characteristics when the polymers wereused as fibrous materials and films as well as the above mentionedaerospace protective coatings.

Coating polymers with generally typical aircraft paint pigments andfillers, as primers and topcoats, gave good results when tested onaluminum panels for one week in a circulating air oven at 500 F.However, when coatings on titanium and steel were given this same test,they became brittle. It was found that replacement of significantquantities of the pigments and fillers with aluminum hydroxide gavepaints which were outstanding on titanium and steel, and also aluminumafter the 500 heat test for one week.

The following specific examples of the invention are intended toillustrate the same but not to limit it in any way:

EXAMPLE I An aromatic saturated linear polyester was made with thefollowing difunctional intermediates, in the molar proportions shown:

25 isophthaloyl chloride 25 terephthaloyl chloride 50% Bisphenol A (BPA)The acid chlorides were dissolved in an organic phase of methylenechloride, and the Bisphenol A in an aqueous phase containing sufiicientsodium hydroxide to form the disodium salt of Bisphenol A. The twophases were then poured along with a slight amount of triethyl aminecatalyst, into a household Waring blender, and vigorously agitated for aperiod of minutes.

The organic phase containing the formed polymer in solution wasseparated from the aqueous phase, washed several times with water andthen was slowly added to vigorously agitated boiling water to coagulatethe polymer. The finely divided product was washed several additionaltimes with water to remove residual impurities and then was dried in anoven.

When evaluated, the polymer was insoluble in nontoxic paint solvents,such as toluene, xylene, ketones and esters, but had limited solubilityin tetrachloroethane and other chlorinated solvents. After severalweeks, however, it was noted that solutions gelled. The tensile strengthof cast films was approximately 10,000 p.s.i., and the elongation atbreak approximately 6%. Coatings, both clear and titanium dioxidepigmented, when applied on aluminum panels and placed in an aircirculating oven for one week at 500 F. were slightly brittle anddarkened some.

Similar pigmented coatings which were weathered in Florida for a periodof three months exhibited some yellowing and chalking.

The polymer was quite tough and abrasion resistant, and had a brittlepoint somewhat below 65 C.

. Coatings showed good resistance to aircraft jet fuels, and also tohot-ester type jet lubricants of the type as specified in FederalSpecification MIL-L-23699.

EXAMPLE II In a manner similar to that used in Example I, a polymer wasprepared with the following difunctional intermediates, in the molarproportions shown.

25% isophthaloyl chloride 25 terephthaloyl chloride 50%hexafiuoroacetone EPA The polymer exhibited poor but improved solubilityin non-toxic paint solvents such as toluene and xylene solutions gelledafter several weeks. Its hot jet lubricant resistance was also poor.Coatings, fibers, films and sheets and other fabricated articles of thepolymer did exhibit excellent outdoor weather resistance. Waterresistance was also outstanding. Coatings on aluminum panels, both clearand pigmented, exhibited outstanding resistance to discloration whentested in an air circulating oven for one week at 500 F.; however, theywere slightly brittle. Pigmented coatings weathered in Florida for threemonths did not darken or chalk.

4 EXAMPLE III A polymer was similarly prepared with the followingdifunctional intermediates, in the molar proportions shown.

15% terephthaloyl chloride 35% isophthaloyl chloride 50%hexafiuoroacetone Bisphenol A The polymer in addition to exhibiting thedesirable characteristics of Example II, had excellent solubility innon-toxic paint solvents, such as toluene, xylene, anisole, and thehigher molecular weight esters and ketones; A 70/30 toluene/xylenesolution did not gel even afterone year extended storage at roomtemperature. Solution viscosities, however, decreased significantly withaccelerated storage at F., indicating some degradation of the polymer toa lower molecular weight. In addition, polymer coatings on aluminumpanels, although they did not discolor, showed some loss of propertiesafter aging in air for one week at 500 F., particularly a tendency tobrittleness. Florida weathering of titanium dioxide pigmented coatingson aluminum panels showed no chalking or discoloration after threemonths.

Jet lube resistance of coatings was poor.

EXAMPLE IV The following polymer was prepared by the above describedprocedure of Example I, using difunctional intermediates in the molarproportions shown below. It will be seen that this polymer was preparedwith a terminator, benzoyl chloride.

l4.8%"terephthaloyl chloride 34.6% isophthaloyl chloride 1.0% benzoylchloride 49.6% hexafluoroacetone Bisphenol A This polymer exhibited allof the desirable characteristics of the polymer in Example III. The use'of the terminator also gave more uniform molecular weight polymer frombatch to batch. Unexpectedly and more significantly, polymer solutionswere stable after accelerated aging for one month at 125 F., thus makingpossible the formulation of high temperature polyester coatings andpaints which have long shelf life.

Just as significant and unexpected, coatings on aluminum panels were notbrittle after aging in air for one week at 500 F., but were almost astough and flexible as original unaged coatings. Florida weathering oftitanium dioxide pigmented coatings on aluminum panels showed nochalking or discoloration after three months.

Isothermal aging data from 450 F. to 650 F. at 50 intervals, between thepolymer in Example III (without terminator) and the polymer in thisExample IV (with terminator) show percent weight losses, andconclusively demonstrated the advantage of the terminator on hightemperature stability for this type of polymer. These data were obtainedon a DuPont thermogravimetric analyzer and are given below.

ISOTHE RMAL HEAT TESTS Percent weight loss after six hour eating in airExample III Example IV 1 Tem perature:

Chemically effective amounts of the benzoyl chloride terminator wereused up to a maximum of two molar percent and similarly, chemicallyeffective amounts of other terminators up to two molar percent were usedwith equally good results as above. These included naphthaloyl chloride, diphenyl carbamoyl chloride, para phenylj phenol tertiary butylphenol and other thermally stable aromatic and he'terocyclicmono-functional materials that are 'fun'ctionalto or react with the endacid groups or end phenolic groups o f the polymer. All of the thermallystable polymer termiuzitors which react with the end f thisty peqflpolymer which we tried were effegtiv to give polymersolutionstability and improved rangehight'empetature stability. Thus, itwas apparen t that,all gerrninators o this type are eifective to give ths typei polymersolution stability and long range high temperatlgre,stability. Similarly, aliphatic mono-functionalte inator s gaye solutionstabilityto this type polymer, d d .not improve long'range' hightemperature polyp er because .oftheirlack of structural stability eqalept tolarornaticand heterocyclic structures. Thus, it is also apparentthat all aliphatic terminators of this type give solution stability tothistype of polymer.

Jet lube resistance was still poor. .-.Iu.stil l' othere gamples, thepolymers of Examples I and II were made with benzoyl chlorideterminators. Solutions gf these-polymers gelled after-several weeks, butpolymer coatings subjected to the 500 F. air oven aging test for oneweek exhibited outstanding heat resistance and'did notembrittle. r-sItis, compl ctely unexpected to find that an aromatictype polymer, .as inExample IV above, exhibits good initial clarityand lack of. color, thatit retains this property after 500? Rheat, sunlighgand generalweathering exposiir and,"if additiori,essentially its other initialphysical properties." p

I EXAMPLE V A polymer was prepared as above, using the difunctionalintermediates, along with a mono-functional termi- 'tt'ator, in themolar proportions shown below.

{14.8% terephthaloyl chloride 34.6% isophthaloyl chloride 1.0%,.benzoylchloride, 1, 44.6%.;hexafiuoroacetone Bisphenol A 5- %--.B p Ql'A 'jlcmtean eifbn eamounts of the Bisphenol A up to fiveniolar percent werealso used with improved re- E hiof the polymers exhibited all of theoutstandipg pro ties ofthe polymer of Example IV. They had good Florida;weathering resistance and did not discolor when in an air circulatingoven for one Week at 500 F.", e solubility of each polymer in non-toxicpaint sol- GEIIIS i'r'em'ained good, but their jet lube resistance,altllgll gll i1t tproved,""was" not satisfactory. At temperaturesbetween 500 to F., they exhibited a slight degree of cross-linking.

. A'zpolymer was prepared-as above, using the followingdifunctionaliintermediates, alongwith a terminator,- in the'mol'ar'proportionsshown.

14.3% terephthaloyl. chloride 34.6% isophthaloyl chloride 1.092;}.benzoyl. chloride 39.6%. hexafluoroacetone Bisphenol A 10.0% Bisphenol'AV The polymer exhibited all of the desirable properties of the polymerin Example V. In addition, coatings showed good resistance to'aircraftjet fuels, and also to hotester-type jet lubricants specified in FederalSpecification MIL-L-23699.

At temperatures between 500 F. and 600 F., the polymer exhibitedsufiicient cross-linking to increase its high temperature capabilityfrom 500 to 570 F. for

long periods of time. Polymers without Bisphenol A did not cross-link.

In related experiments, the Bisphenol A was used to replace thehexafiuoroacetone Bisphenol A in 20% increments until total replacementoccurred. In all cases, the excellent heat resistant characteristics ofthe polymer were maintained and cross-linking could be controlled asrequired with temperature, time and Bisphenol A con tent. Inapplications where discoloration resistance from weathering or heat wasimportant, about 10% Bisphenol A was the maximum that could be used.

In still other related experiments where excellent heat resistance wasrequired but where discoloration resistance from weathering or heat wasnot required, the hexafiuoroacetone Bisphenol A was partially or totallyreplaced with other Bisphenols, 4,4-dihydroxy|diphenyl ether,4,4-dihydroxydiphenyl, 4,4'-dihydroxydiphenol methane, or combinationsof any of these.

EXAMPLE VII A polymer was prepared as in Example VI above but with 7.5molar percent Bisphenol A, as shown in the molar proportions below.

14.8% terephthaloyl chloride 34.6% isophthaloyl chloride 1.0% benzoylchloride 42.1% hexafiuoroacetone Bisphenol A 7.5% Bisphenol A Thepolymer exhibited all of the outstanding characteristics of the ExampleVI polymer, including jet lube resistance.

In similar experiments to the above example, it was determined that theratio of iso-/terephthaloyl chloride could be varied from /5 to 60/40and still give satisfactorily soluble polymers for high temperaturepaints with all of the outstanding characteristics of the above polymerof Example VII. The preferred ratio of iso-/ terephthaloyl chloride,however, was 70/30 as used in Example VII.

In still other related experiments, using either essentially 50 molarpercent hexafiuoroacetone Bisphenol A or up to 20 molar percentreplacement of the hexafiuoroacetone Bisphenol A with Bisphenol A, itwas further noted that these excellent weathering and heat resistantcharacteristics were maintained with the above type of polymer ofExample VII, when the phthaloyl chloride intermediates used were allisophthaloyl chloride or all terephthaloyl, or any combination thereof.This was also true of the use of orthophthaloyl chloride although eitheror both of the other two phthaloyls were preferred in making polymercompositions.

EXAMPLE VIII The following polymer was prepared. as above, withintermediates in the molar proportions shown below.

14.8% 2,6 naphthaloyl chloride 34.6% isophthaloyl chloride 1.0% benzoylchloride 49.6% hexafiuoroacetone Bisphenol A The above polymer hadoutstanding heat and weathering resistance, similar to the polymer ofExample IV. It was particularly noted and unexpected that this and othersimilar polymers containing the naphthalic unit were more more resistantto gamma radiation than those containing only the phthalic unit.

Polymers prepared using major proportions of 2,6 naphthaloyl chlorideand also total replacement of all the phthaloyl chlorides with thisintermediate, continued to exhibit outstanding heat and weatheringresistance, and also as coatings, sheets, films, fibers, and otherfabricated articles. This was true of these polymers also when they wereprepared using essentially 50 molar percent hexafluoroacetone BisphenolA or up to molar percent of its replacement with Bisphenol A. Similarpolymers made using greater than 20 molar percent to total replacementof the hexafiuoroacetone Bisphenol A with Bisphenol A exhibited theoutstanding heat resistance but not the weathering resistance.

EXAM'PLE IX This polymer was prepared as above, with the followingdifunc-tional intermediates, along with a terminator, in the molarproportions shown below.

14.8% bibenzoyl chloride 34.6% isophthaloyl chloride 1.0% benzoylchloride 49.6% hexafiuoroacetone Bisphenol A The polymer had outstandingheat and weathering resistance similar to the polymer of Example IV.Polymers prepared using major proportions of the bibenzoyl chloride andalso total replacement of all the phthaloyl chlo rides with thisintermediate, continued to exhibit outstanding heat and Floridaweathering resistance. This was true of these polymers also when theywere prepared using essentially 50 molar percent hexafluoroacetone Bis:phenol A or up to 20 molar percent of its replacement with Bisphenol A.Similar polymers prepared using greater than 20 molar percent to totalreplacement of the hexafiuoroacetone Bisphenol A with Bisphenol Aexhibited the outstanding heat resistance but not outstanding weatheringresistance.

EXAMPLE X- This polymer was prepared with the following intermediates,in the molar proportions shown below.

14.8% oxydibenzoyl chloride 34.6% isophthaloyl chloride 1.0% benzoylchloride 49.6% hexa fiuoroacetone Bisphenol A This polymer also hadoutstanding heat and weathering resistance similar to the polymer ofExample IV. Polymers prepared using major proportions of oxydibenzoylchloride and also total replacement of all the phthaloyl chlorides withthis intermediate continued to exhibit outstanding heat and Floridaweathering resistance. This was true of these polymers also when theywere prepared using essentially 50 molar percent hexafluoroacetoneBisphenol A or up to 20 molar percent of its replacement with BisphenolA. Related polymers prepared using greater than 20 molar percent tototal replacement of the hexafluoroacetone Bisphenol A with Bisphenol Acontinued to exhibit the outstanding heat resistance but not theweathering resistance.

EXAMPLE XI The polymer of Example VII was used in the followingformulation to prepare an aircraft primer paint.

Primer (a) Ingredient: Percent composition Polymer 40 Strontium chromate32 Titanium dioxide 6 Talc 14 Silica 8 The polymer of Example VII wasalso used to formulate a gloss-white topcoat, in the followingproportions.

Gloss-white topcoat The required solvents were added to the above (a)and (b) formulations and the ingredients were ball-milled for six daysto give finished paints. The primer, followed-by the topcoat were thenspray-appliedon aluminum; titanium, and stainless steel panels, whichhad first been given proper chemical'pretreatments'After several days;air-drying at room temperature," the panels were placed in a circulatingair oven at 500 'F. for one 'weekrEx amination of panels after thetestshowed no discoloration on any panels. Coatings on aluminum panelswere flexible and adhesion was good. Coatings on titanium and stain lesssteel were somewhat brittle and a'dhesion'was only fair. 7 Y

EXAMPLE XII The polymer of Example VII was usedin the following aircraftprimer paint in the proportions shown below. It will be noted that thisprimer contained :aluminum hydroxide. Y .7

The polymer of Example VII was again-used, to far-- mulate a gloss-white'topooat, containing aluminumhy droxide, in the proportions shown below;1

Gloss-white topcoat (b) Ingredient: Percent composition Polymer 5Titanium dioxide 25 Aluminum hydroxide 10 The required solvents wereadded to the above" (a) and (b) formulations and the'ingredien-ts we'reball-milled six days to give finished paints. The primer, followed'bythe topcoat were then spray-applied on aluminum, titanium, and stainlesssteel panels, whichhad firstbeen given proper chemical ptetreatments.After several days, air-drying at room temperature, the panels wereplaced in a circulating air oven at 500 F. for one week. Examination ofthe panels after this heat test showed be dis coloration on any panels.Coatings on aluminum'fpanel's were quite flexible and adhesion wasoutstanding. panels in all respects equalled original 'tina'g e'd"panel's. Coatings on the titanium and stainless steel panels 'wereunexpectedly quite outstanding. They maintained their flexibility, hadexcellent adhesion, and in every way were equal to the original panels.

Original panels of the above coatings. onaluminum, titanium andstainless steel unexpectedlyhad superior jet lube resistance to thecoating. compositions of Example XI which did not contain aluminumhydroxide.

In other experiments with primer 'compositions'"and topcoat compositionssimilar to the above; itwas shown that beneficial elfects are obtainedin'the primer and top coat when the aluminum hydroxide replacestro'm 10%to of the inorganic ingredients 'of the primerarid topcoat.

What is claimed is: A

1. A polyester product obtained from the reaction of essentially 50molar percent of 4,4'-hexafluoroisopropylidene diphenol, essentially 50molar percent of at least one of the chloride group consisting ofisophthaloyl chloride, terephthaloyl chloride, naphthaloyl'dichloride,dibenzoyl chloride, and oxydibenzoyl chloride, and between 1 and 2 molarpercent of at least one mono-functional 9 polymer terminator of thegroup consisting of benzoyl chloride, naphthaloyl chloride, p-phenylphenol and carbamoyl chloride.

2. The polyester of claim 1 in which the chloride of the chloride groupis composed of isophthaloyl and terephthaloyl chloride.

3. The polyester of claim 1 in which the chloride of the chloride groupis composed of between 5 to 40% terephthaloyl chloride and between 60 to95% isophthaloyl chloride.

4. The polyester of claim 1 in which the chloride of the chloride groupis naphthaloyl dichloride.

5. The polyester of claim 1 in which the chloride of the chloride groupis bibenzoyl chloride.

10 6. The polyester of claim 1 in which the chloride of the chloridegroup is oxydibenzoyl chloride.

References Cited UNITED STATES PATENTS 3,388,097 6/1 968 Cramer 260473,160,602 l2/ l964 Kantor et al. 26047 3,216,970 Ill/1965* Conix 260473,317,464 5/1967 Conix 26047 LESTER L. LEE, Primary Examiner US. Cl.XJR.

l17-132 R, 161 K; 26031.2 XA, 32.8 R, 33.2 R, 33.6 R, 33.8 R, 47 C

